Apache 57 servo question

[KevB]

Hi.
After many years of my Zenoah powered Apache sitting unused, I've decided to convert it to brushless.
The electrics I'm using are:
SSS 5694 1000kv.
Seaking 300a HV V4 esc.
I plan to use a range of batteries from 6S up to 12S. (Dependant on the water I'm running on at that time and who I may be handing the tx over to... hahaha)

The question I have is considering that 'normal' size servos are available much torquier than they used to be, is it still the 'done thing' to use 1/4 scale servos for the rudder or are the higher torque normal servos up to the job? The boat will be used in a mixture of conditions and not just mirror flat lakes....

[Mike W]

12S/1000KV will be a dangerous combination on a 57" V hull. Be very careful with loading. I'd fix a RPM setup (~30k) suitable to the prop diameter range that hull will require then prop the boat appropriately for water conditions. At 1000KV on that hull my limit would be 8S. Maybe switch to a Hydra at 1000KV for more current handling capacity on 8S or reduce KV to 675-700 for that SK ESC and go 12S.

Use a standard size 40kg servo. And don't give away torque and resolution by reducing ATV to make up for a poor mechanical setup that results in excessive travel. In all cases I have to drill a servo arm hole inboard of the nearest one provided to achieve this.

[KevB]

Thanks for the info Mike.
Do you mean dangerous as in an expensive puff of smoke?
I wasn't planning on using the props I used with the Zenoah, I've changed the shaft to one that's stepped down to 3/16th at the end to allow for smaller props. I have a selection ranging from 54mm up to 63mm to try.
Am I right in assuming that a smaller prop will reduce the load but the downside is an increase in the risk of over-revving?

I'm not after all out speed, and may, if the performance is ok, run it on 6S as I have several packs already, but, for the sake of it, I would like to run at higher cell counts occasionally just to 'know' it can do it...

And yes, I understand what you mean by not using ATV to compensate for a bad installation... My rc days started way way before ATV was a thing and have always preferred to do the adjusting at the servo arm. If the conditions dictate less throw then I'm just lighter on the sticks... (Yes, I use stick radios, I've never felt happy with a wheel and a trigger, I feel they give you less control, and that a trigger is for either a gun or a slot car.... hahahaha)

[Mike W]

Yes you are correct on all counts and you are aware of the risks. Those props are on the small end of the range for that boat but will be fine for sport use but with higher slippage.

[fweasel]

I use a cheap DSS 35kG digital servo in my 60" Epic V-bottom. I normally use higher end servos on my SAW cats for speed and precision, but have been satisfied with the DSS.

1000kV on 12S is too much RPM. I ran a TP5680 650kV on 12s in my 60" Epic and it was in the mid 60's which was too fast for the water conditions I built the boat to run in. I dropped down to 10S and got into the 50's with a smaller prop, but ultimately went all the way down to 5S and a much larger gas sized prop. It was just a tad too slow in the rough water, so I swapped in a 850kV TP5680 to get a little speed back running the same gas prop (Prather 275). I run my lipos in parallel to get longer run times and have about 18,000 mAh on board.

[KevB]

Many thanks to you both for this valuable info, it's much appreciated.

I guess I'll probably be happy with it on 6S after what I've just read, and, as Mike said, prop it for the conditions.
I wasn't intending to use the gas prop I used to use on it with the Zen, but would an X470 actually be ok with this motor on 6S? I suspect it may be too much , but you guys have the experience to be able to advise me...

[fweasel]

6S and a 1000kV motor will be right around 22Krpm ish, which is near the top of of a gas setup give or take, so a 470 prop would work. Start slow, check temps, make sure cooling is working and the hull isn't running too wet which causes more drag and load on the motor.